1. Technical Field
This invention relates to the field of personal communications devices, and more particularly, to improving audio signal quality in personal communications devices.
2. Description of the Related Art
The use of personal communications devices has become widespread. Examples of such devices can include cellular telephones, portable telephones, voice-enabled personal digital assistants, devices having a handset component, and the like. These devices not only facilitate communication between users and provide services as standalone units, but also can serve as an interface, or the first signal processing stage, for larger distributed voice-enabled systems. Notably, voice-enabled services often require a minimal level of audio signal quality for accurate performance. Accordingly, the use of a personal communications device which lacks the ability to produce an audio signal having a minimal quality can significantly limit the performance of a voice-enabled system. For example, in the case of a communications system, low quality audio signals can result in miscommunication between users. With regard to speech processing, low quality audio signals can lead to mis-recognized words.
Several factors can influence the quality of an audio signal generated by a personal communications device. One factor can be the distance between an audio speech source, such as a user's mouth, and the transducive element of the personal audio communications device. Typically, the distance between the audio source and the transducive element of the device changes over time as the user shifts body positions. For example, as a user speaks into a cellular telephone, the user can look about in various directions or inadvertently take the telephone away from the user's ear or mouth. As this distance changes, the audio characteristics of the user's speech also change over time. In particular, as the distance becomes smaller, the detected volume of the user's speech can increase. Thus, with the audio source located closer to the personal communications device, a higher quality audio signal having an increased signal to noise ratio can be generated by the personal communications device. As the distance increases, however, a lower quality audio signal having a lower signal to noise ratio can result.
The distance between a user and the personal communications device also can affect the user's ability to hear audio generated by the personal communications device. Notably, as the distance between the user and the personal communications device grows larger, the perceived volume of the audio generated by the device decreases. Thus, distance not only can affect the quality of audio signals generated by personal communications devices, but also can affect the user' ability to hear audio produced by the device.
Another factor which can affect audio signal quality can be the environment in which the device is used. By their nature, personal communications devices can be used in a wide variety of situations and environments with varying levels and sources of background noise. Moreover, unwanted or undesired sounds generated from various sound sources within an audio environment, referred to as background noise, can emanate from differing locations within that audio environment. Common examples can include, but are not limited to, automobile noise or other voices within a crowded public place. Regardless of the source, the inability to distinguish a desired speech signal from background noise can result in audio input signals having decreased signal to noise ratios.